Hi Jonathan,
Another troubleshooting step you can perform is updating the BIOS of the motherboard. You can find BIOS updates on this link http://www8.hp.com/us/en/support-drivers.html.
If the issue persists I recommend contacting HP in order to check if they have disabled the option to create RAID 5 volumes in that specific computer model.
If you do not find any option in the BIOS related to Intel Rapid Recovery then there is a chance HP has hidden that option so; nobody can change it.